The great thing about jailbreaking (and no, it's not this) is that a lot of smart people take a look at the capabilities of the iPhone and wonder how come nobody made a (insert program here) yet? And then go and develop said program.
Case in point: A p2p client for the iPhone
iSlsk, developed by Eric Castro, is Soulseek in native app form for the iPhone. It uses the Soulseek network to let iPhone (+iPod touch) users share songs with one another. Once the songs are downloaded, iSlsk imports them into your iTunes library for seamless playback. There is a lot of promise in such a program, imagine being able to download whatever you want, whenever you want.
There are still a lot of kinks in the programming, in fact, I couldn't even manage to start a download due to some bug. But reports are floating that Wi-Fi averaged 20 Kbps while the EDGE network ran about half that. Soulseek doesn't have the install base of a Limewire and is more known for being a hot bed for indie artists but this is a great first effort into implementing a p2p client for the iPhone. Expect more updates soon.